Technical Field
The present disclosure relates to a pneumatic tire, and in particular relates to a pneumatic tire with which it is possible to obtain satisfactory drainage performance while reducing air column resonance sound by forming flexible fences in the main groove of the tread.
Background Art
Air column resonance sound in a main groove formed in a tire tread is generated as a result of resonance in a tube (air column) formed by the main groove and the road surface, and the resonant frequency thereof depends on the length of the air column formed between the main groove and the road surface.
This air column resonance sound manifests itself in the form of noise inside and outside the vehicle, and its peak is often at around 1 kHz, which readily reaches the human ear. As a technique for reducing the air column resonance sound of a main groove a technique is known whereby the air column resonance sound is reduced by interrupting the flow of air in the direction in which the main groove is formed, by providing so-called flexible fences, in other words protrusions, which extend from the bottom or the walls of the main groove, blocking all or most of the main groove. However, interrupting the flow of air in the direction in which the main groove is formed also interrupts the flow within the main groove of water that penetrates into the main groove when being driven on a wet road surface, and because there is a deterioration in the drainage characteristics of water interposed between the pneumatic tire and the road surface, handling stability on wet road surfaces deteriorates.
FIG. 4 of patent literature article 1 discloses a technique which achieves both drainage and a reduction in air column resonance sound by disposing within a main groove three groove fences 3 (flexible fences) spaced apart from each other and extending respectively from the groove bottom and from opposing groove walls within the groove.
Also, FIG. 3 of patent literature article 2 discloses a technique which achieves both drainage and a reduction in air column resonance sound by disposing separating walls 30 (flexible fences), which extend from the bottom of a main groove, in such a way that the greater part thereof, starting at the opening of the main groove, does not touch the groove walls.